This invention relates to devices for working concrete surfaces, and more particularly to a vibratory device of the hand-held float type.
A wide variety of tools exists in the art for working cementitious materials into a finished form including various forms of bull floats, hand floats, and speciality tools including edgers, joiners, and trowls. In a typical job, a layer of wet concrete will be delivered to the work situs, whereupon the worker will commence spreading the concrete into a desired layer by means of shovels, screeding devices, also well known in the art, and the like. After the concrete is thus spread into the generally desired form, a process of generally compressing and further smoothing the concrete layer may thence begin by means of a large bull float or the like extending from an elongate handle. Next, more detailed work frequently commences, generally by means of a hand-held float in attempting to further compact the concrete for purposes including the driving of suspended gravel downwards, and developing a wetted surface slurry or soup-like finish, whilst further driving out air pockets and the like for preparing the surface for final finishing. Thereafter, when the surface slurry is thus formed, it is conventional to employ a smoothing or finishing trowl to develop a very smooth surface and to employ the aforementioned specialty tools such as edgers or the like for providing finishing touches to the work such as curved edges or the like.
It is generally known that concrete which is usually composed of an aggregate of cement, sand, gravel, rock of graded or miscellaneous sizes, and water, when mixed and layed or poured, generally contains voids which if not tamped or worked would not result in a desired homogeneous body. Moreover, the surface would take on a highly undesirable rough and uneven finish which, after partial setting of the concrete, would render the surface difficult if not impossible to finish to the desired smooth and even consistency. This is particularly the case with drier mixes wherein pieces of rock or gravel of the aggregate may have an even greater tendency to remain close to or above the desired final surface so as to interfere with any final finishing, leveling, or other contouring or smoothing operations as aforesaid.
For this reason, it has long been known in the art that in the act of providing a first general compacting, tamping, screeding or other such operation following the laying or dumping of the mix, various large vibrating devices may be benefically employed. Illustrative embodiments of such large vibrating tampers or the like may be seen in U.S. Pat. Nos. 3,306,174 to Wardell, 2,289,248 to Davis, 1,955,101 to Sloan, and 2,209,656 to Mall. These devises generally include a rather large flat base plate surface having disposed thereon a heavy and bulky vibrating means with an elongate handle having the appearance of a broom handle or the like attached thereto for moving the large plate across the concrete surface. Such devices are obviously intended for providing a first, general smoothing and compacting operating over a large area.
When the worker has progressed to the aforementioned finishing stage wherein it is desired to provide a highly smoothed surface finish, a variety of vibrating hand trowels have also been provided and employed with varying degrees of success. Representative examples of such trowels which are primarily for smoothing or finishing work, may be seen represented in U.S. Pat. Nos. 3,376,798 to Bodine, 2,514,626 to Clipson, and 2,411,317 to Day et. al. Whereas such trowels are, in contrast to the aforementioned larger devices, intended for hand-held operation, they retain several characteristics of the larger apparatus such as being of a rather awkward large and heavy construction, illustrative of which is the trowel disclosed in the Day patent. Whereas such features may in fact be beneficial with respect to the larger devices, in a hand-held tool this bulk, weight, and complexity may render the tool totally impractial for use, particularly in view of the fact that the operator is typically working for long periods of time on his knees and often in awkward positions. It must be recognized that these trowels are conventionally used primarily in the finishing operations wherein a great deal of vibratory energy is not required inasmuch as a mere final smoothing of the surface slurry is being effected. In these instances, a much less bulky vibrating means might be provided although, as aforesaid, most designs nevertheless continue to suffer from undue weight, bulk and the like, notwithstanding that a variety of such vibrating means have been attempted to be employed including plunger-type vibrators, (as disclosed in the patent to Clipson), air driven turbine vibrators, as disclosed in the patent to Day, and even sonic air-driven orbiting-mass type vibrators as illustrated in the patent to Bodine.
lt will be recalled that in the stage of forming concrete between the use of the large spreading and compacting devices and the finishing work provided by trowels and specialty tools, an intermediate floating operation is nevertheless frequently necessary wherein a hand-held float is employed. In this operation it is conventional to hand-tap the concrete surface as aforesaid to drive the rock and gravel aggregate downwards and to bring a slurry to the surface for the final finishing operation. In such an intermediate operation, a relatively more substantial amount of force must be imparted to the mixture to achieve these objectives than is necessary to effect the final finishing with the finish trowels in the manner previously described. It will be appreciated that this intermediate step can become quite laborious and exhausting when large surfaces are involved. Moreover, and often more serious, is the fact that concrete will begin the setting process often very rapidly such that if this intermediate step is not performed within the required time, an unsatisfactory result is obtained.
Accordingly, it would be highly desirable to provide a hand-held cement float of an automatically vibrating variety for purposes of performing this intermediate hand-held floating step wherein a substantial vibratory energy is imparted to the concrete surface. However, as previously mentioned, existing hand-held vibratory trowel devices have been unsuited for this application for a number of reasons. Not only have such trowel designs been found impractical due to their large weight and bulk, but they have further been found unsatisfactory in delivering an approporate amount of vibratory energy to effect the development of the slurry and downward movement of the suspended rocks and gravel. It was accordingly thought such a hand-held vibrating float could not be provided which was at the same time compact, light in weight, and of an extremely simple and uncluttered design, yet at the same time employing a particular vibrating means capable of delivering sufficient vibratory energy to accomplish the objectives of the intermediate floating step. Nevertheless, these objectives and features have been obtained with the present invention which will appear as the description of a presently preferred form of the invention in a simple and illustrative form proceeds with reference to the accompanying drawings.